chuck thread size

[mick70Participant @mick70]

picked up load of bits today from where i bought my southbend lathe.

with stuff is a pratt bernard 4 jaw independent chuck now thread is lot smaller than stuff on southbend.

anyone know what size thread is likely to be?

havent got any bore gauges and thread starts fair way down hole.

thanks

[mick70Participant @mick70]

[JasonBModerator @jasonb]

[Ian PParticipant @ianp]

Posted by JasonB on 26/04/2015 17:06:53:

The piece I have is much longer

[JohnFParticipant @johnf59703]

Educated guess, if the thread is in the chuck body and not a backplate attached to the chuck it is quite likely to be a "Myford" thread. That is 1 1/8" x 12tpi Whit form.

May of course be something completely different !

[paul 1950Participant @paul1950]

if is the chuck with the built in thread its not worth much and if was mine i would bin it. bee caught out with chuck thread sizes before. sold a southbend chuck to someone with a boxford lathe and it came back. it screwed on nearly all the way but not all the way.

[BazyleParticipant @bazyle]

Southbend lathe is UNC 60 degree while Boxfod is Whitworth 55 degree though tpi is the same.

A built in thread is good in many ways as it reduces overhang.

Cut a piece of thickish cardboard to a taper spanning the rough sixe of the hole. Screw it in and it will be marked up with the tread spacings at the core diameter of the thread. Make a few adjustments and you know the parameters. Do a bit of googling and you know what the chuck is off. You can also use bits of soft wood, like balsa bits of wood with plasticine on them, a few brain cells helps too.

Edited By Bazyle on 26/04/2015 18:45:10

[JasonBModerator @jasonb]

If its in reasonable nick I would not be throwing it away, With second hand 4-jaws with threaded bodies fetching £100 thats worth finding out what the thread is. And if its a back plate one then with a new backplate it will fit your lathe.

Stick up a couple of photos showing teh ref number of teh chuck and what dia it is.

 

J

Edited By JasonB on 26/04/2015 18:49:25

[mick70Participant @mick70]

the numbers on it are.

e12380

1548

and 16130

.

[mick70Participant @mick70]

would rather find size then try to make adaptor so i can use it.

[mick70Participant @mick70]

its a 6" dia.

threaded section is part of chuck no backplate.

[BazyleParticipant @bazyle]

Posted by naughtyboy on 26/04/2015 19:07:44:

would rather find size then try to make adaptor so i can use it.

That's the spirit

[Clive FosterParticipant @clivefoster55965]

If its lots smaller than the Southbend size it could be 7/8 diameter by 9 or 12 TPI as used on small spindle Myford ML 1 to 4 series machines, related Drummonds and other makes. Threaded back 4 jaws of 6" diameter with relatively small mounting threads were not uncommon. I've had a couple or three through my hands over the years despite never having a machine they would fit! Second and third photos down on this **LINK** shows an example on a nicely re-furbed ML2.

Before you make an adapter it might be worth investigating to see if the body can be bored out to take the larger thread.

Clive

Edited By Clive Foster on 26/04/2015 21:00:01

[RobboParticipant @robbo]

Measure the plain part of the hole before the threads, you can reach that with a vernier/digital caliper.   Not the most accurate but near enough for now.

If it measures 1.24" – 1.25" that's the size for a Myford 7 series register.

Edited By Robbo on 26/04/2015 21:07:20

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